The present invention relates to flame retardant polypropylene resin compositions. More particularly, the present invention relates to flame retardant polypropylene resin compositions which principally contain polypropylene resin. The compositions are fabricated without generating corrosive gas or toxic gas, the fabrication quality is little lowered, the fabricated articles are very fire retardant, and the bleeding of the fire retardant additive to the surface of the fabricated articles is slight under high humidity conditions.
Hitherto, polypropylene resin is widely used in fields of household electric appliances, buildings, interior decoration, automobile parts, etc., because the resin has good processing characteristics, chemical resistance, weathering resistance, electrical properties and mechanical strength.
Polypropylene resin is naturally flammable. However, there have been growing demands for flame retardant materials having many uses. For filling these demands, several kinds of flame retardant polypropylene resin compositions have been provided.
As such flame retardant polypropylene resin compositions, the following compositions are exemplified; a composition obtained by adding hydrous inorganic compounds, for example, magnesium hydroxide, aluminium hydroxide or hydrotalsite to polypropylene resin as shown in Japanese Laid-open Patent Publication Nos. 53-92855, 54-29350, 54-77658, 56-26954, 57-87462, 60-110738, etc., a composition obtained by adding polyethylene having a melt index of 0.01-2.0, a halogen compound such as decabromodiphenyl ether or dodecachloro-dodecahydromethanodibenzocyclooctene, and one or more inorganic fillers selected from the group consisting of powder talc, kaolinite, celesitite, silica and diatomite to polypropylene resin as shown in Japanese Patent Publication No. 55-30739 and a composition obtained by adding ammonium phosphate (or amine phosphate), a reaction product of a nitrogen compound containing &gt;C.dbd.O (or &gt;C.dbd.S or &gt;NH) which is inserted in a ring structure and an aldehyde or an oligomer (or a polymer) of a 1,3,5-triazine derivative to poly-propylene resin as shown in Japanese Laid-open Patent Publication Nos. 52-146452 and 59-147050.
However, in the composition obtained by adding a hydrous inorganic compound such as magnesium hydroxide to polypropylene resin, to obtain high flame retardance, it is necessary to add a great quantity of the hydrous inorganic compound, and as a result the moldability of the composition deteriorates.
When the composition obtained by adding a halogen compound to polypropylene is used, the moldability is not so bad, and the composition has high flame retardance. However, the composition has problems that corrosive gas and toxic gas are produced in the fabrication or in the combustion.
Further, when the compositions disclosed in Japanese Laid-open Patent Publication Nos. 52-146452 and 59-147050 are used, the lowering of fabrication quality of the compositions is relatively small, and the production of corrosive gas and toxic gas is little.
However, the composition shows a flame retardant rank or rating of V-0 at a thickness of 1/8 inches by using a test (abbreviated as UL94 vertical burning test hereinafter) based on the vertical burning test of "Flammability test of plastic materials for instrument parts" of UL subject 94 (Underwriters Laboratories Incorporation). However, in the 5V test in which higher flame retardance is required, it is difficult to obtain a high flame retardant rating of 5V at a thickness of 1/8 inches, because drops drip and combusted pieces fall by melting (these drops and falling bodies are abbreviated as drops and the nature that causes dripping is abbreviated as drip characteristics), and it is also difficult to obtain a high flame retardant rating of V-0 at a thickness of 1/32 inches. Further, since ammonium phosphate or amine phosphate in the compositions has moisture-adsorption characteristics, the bleeding of ammonium phosphate or amine phosphate frequently occurs on the surface of the articles molded under very moist conditions, for example, in the rainy season. As a result, there is a problem in that the compositions are unsuitable for use as electrical insulating materials under such conditions, because the electrical resistance of the molded articles is greatly reduced.
The inventors of the present invention carried out research for resolving the above problems and obtaining flame retardant compositions of polypropylene resin which are highly flame retardant and show a flame retardant rating of 5V at a thickness of 1/8 inches or V-0 at a thickness of 1/32 inches by using a test (abbreviated as UL94 vertical burning test hereinafter) based on the vertical burning test of "Flammability test of plastic materials for instrument parts" of UL subject 94 (Underwriters Laboratories Incorporation). When the compositions are fabricated or burnt, corrosive gas and toxic gas are not produced. They also carried out research for obtaining compositions that corrosive gas and toxic gas are not produced and the lowering of the fabrication quality is little in fabricating or burning them, and the bleeding of flame retardant additives to the surface of the articles molded from the composition is very little under high humid conditions, for example, in the rainy season.